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muting circuit to eliminate turn-on thump
muting circuit to eliminate turn-on thump
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Old 8th January 2019, 04:39 PM   #1
keilau is offline keilau  United States
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Default muting circuit to eliminate turn-on thump

I am looking for a mute-delay relay circuit for a preamplifier. Any drawback to use one designed for loudspeakers?

Stereo Loud Speaker Protection Board 10A Two-Channel 3S Delay Soft Start Circuit 699914281829 | eBay
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Old 8th January 2019, 05:27 PM   #2
rayma is online now rayma  United States
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Quote:
Originally Posted by keilau View Post
I am looking for a mute-delay relay circuit for a preamplifier. Any drawback
to use one designed for loudspeakers?
That's a series switch, instead you want a shunt switch that shorts each output
to ground through series resistors. An example:
Preamp Muting Circuit | audioXpress

Last edited by rayma; 8th January 2019 at 05:56 PM.
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Old 8th January 2019, 06:32 PM   #3
johnhenryharris is offline johnhenryharris  United States
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Hi keilau,
You could use a voltage comparator driving a small relay. the comparator would have a pair of resistors on one input as a voltage divider and a resistor to Cap on the other input. The time to charge the cap and match the voltage on the divider can be varied by using a mulit-turn pot to slow the cap charging. If is much like the delay on a soft start circuit. If you need a schematic I can draw one up for you.
Have a good one.
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Old 8th January 2019, 07:19 PM   #4
Bare is offline Bare  Canada
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Could? also find a Pre that Does Not have a turn on thump problem?
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Old 8th January 2019, 09:34 PM   #5
johnhenryharris is offline johnhenryharris  United States
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Better to follow the process of turning on the preamp first then the power amp, and turning off the power amp first then the preamp. Just easier on the speakers.
I also prefer to have a delay connection on the input to the power amp, so the inputs are shorted until the amp is up and running, this protects the input circuit from spikes on cable connection and static problems. Just an idea.
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Old 9th January 2019, 03:52 AM   #6
keilau is offline keilau  United States
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Quote:
Originally Posted by rayma View Post
That's a series switch, instead you want a shunt switch that shorts each output
to ground through series resistors. An example:
Preamp Muting Circuit | audioXpress
An excellent point. Thank you for the link.
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Old 9th January 2019, 04:06 AM   #7
Halauhula is offline Halauhula  United States
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Transcendent Sound sells a muting kit for preamplifiers.

>>>>>>Muting Circuit Mod

Recommended for Solid State Amps - $35

Here is a muting circuit that provides about a 15 second mute delay during turn-on for the Grounded Grid Preamp or any audio device that has 12 volts DC available. The circuit draws only 60 mA at 12 VDC allowing it to be installed in most any component. The circuit board is prewired. All that is required is to mount the board and terminal strip with three components and wire it up. The device does not interfere with the audio signal at all. Upon shut down, the mute function operates immediately thereby preventing any transients as circuits power down.<<<<<
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Old 9th January 2019, 02:23 PM   #8
keilau is offline keilau  United States
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Default Muting Circuit Mod

Quote:
Originally Posted by Halauhula View Post
Transcendent Sound sells a muting kit for preamplifiers.

>>>>>>Muting Circuit Mod

Recommended for Solid State Amps - $35

Here is a muting circuit that provides about a 15 second mute delay during turn-on for the Grounded Grid Preamp or any audio device that has 12 volts DC available. The circuit draws only 60 mA at 12 VDC allowing it to be installed in most any component. The circuit board is prewired. All that is required is to mount the board and terminal strip with three components and wire it up. The device does not interfere with the audio signal at all. Upon shut down, the mute function operates immediately thereby preventing any transients as circuits power down.<<<<<
I went to browse the Transcendent Sound website but could not find the item you referred to. Can you provide a direct link? Much appreciated.

Your description sounds good. Can you post a schematic and the BOM?
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Old 9th January 2019, 06:25 PM   #9
Halauhula is offline Halauhula  United States
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I don't have the schematic and BOM. It is a kit so no blank boards as I recall. The board is mentioned in the text of the grounded grid pre-amp. I think you need to contact Bruce Rozenbilt directly to buy it separately. It used to be listed as its own separate product but in the website re-design that occurred over winter, the separate listing was removed.
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Old 9th January 2019, 11:11 PM   #10
keilau is offline keilau  United States
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Default UPC1237

Using an UPC1237 IC, it is easy to hand wire the AudioXpress circuit that RayMa suggested. I can buy a headphone protection circuit board kit on ebay and get all the parts I need for $10. Modify the board or hand wire it would be very easy.

Thank you for everyone's suggestion.
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